1. Field of the Invention
The invention relates generally to the use of Fast Fourier Transformations (FFT) for the visual identification of faults in roller bearing elements, by analysis of ultrasonic frequency emissions resulting therefrom.
2. Description of the Related Art
Ultrasonic sensors have been used in the past to detect ultrasonic energy generated by friction within mechanical devices, such as that created by deteriorated bearings, as disclosed in U.S. Pat. No. Re. 33,977 to Goodman, et al., the contents of which are hereby incorporated herein by reference in their entirety. The greater the amount of friction, the greater is the intensity of the generated ultrasonic energy. Applying a lubricant to the device reduces friction and consequently reduces the intensity of the generated ultrasound. Measuring ultrasonic energy thus provides a way to determine when lubrication has reached the friction generating surfaces. Additionally, faulty devices, such as bearings, generate a higher level of ultrasonic energy than do good bearings and thus, whether the bearings are good or bad can also be detected.
In the past, decisions have been made on when to lubricate bearings based on the amount of time that has passed since the last application of lubricant and the specific amount of lubricant added at that time. Typically, this information was compared to manufacturer's recommendations. However, a major reason for bearing failure is improper lubrication, not just a failure to lubricate. In particular, over lubrication can be a problem. It is known in the art to combine a lubrication tool with an ultrasonic detector to help control the application of lubricant to bearings. Such devices are disclosed in U.S. Pat. No. 6,122,966 and No. 6,339,961 of Goodman et al., the contents of which are incorporated herein by reference in their entirety.
As indicated in U.S. Published Patent Application US2006/0209632-A of Goodman, the details of which are hereby incorporated herein by reference in their entirety, both motors and electrical discharges in electrical cabinets used in large facilities may be positioned at widely separated locations. Thus, in order to monitor these motors and cabinets, maintenance personnel need to travel to these locations to make the ultrasonic tests. Thus, a route of travel needs to be defined, and the ultrasonic equipment must be portable and should be light weight, but still have the capacity to conduct the necessary tests.
Since acoustic energy created by faulty bearings is detectable in both the audible and ultrasonic frequency ranges, wherein the ultrasonic range is generally defined to be in the range of 28 kHz to 40 kHz, in noisy environments the audible components are too difficult to detect with the unaided human ear. However, the ultrasonic component is easily detected and located. Thus, means are typically provided for heterodyning, or demodulating, the detected ultrasonic signal into the audio range, and various schemes are available for doing this.
When using ultrasonic energy to detect leaks, deteriorating bearings, electrical discharges or other malfunctions, it is useful to have a portable ultrasonic sensor which indicates the presence and intensity of ultrasonic energy both visually and audibly. U.S. Pat. No. Re, 33,977 to Goodman et al. discloses an ultrasonic sensor that displays the intensity of the detected signal on an output meter operable in either linear or logarithmic mode, and also provides for audio output through headphones. U.S. Pat. No. 4,987,769 to Peacock et al. discloses an ultrasonic detector that displays the amplitude of the detected ultrasonic signal on a ten-stage logarithmic LED display. However, the detector disclosed in Peacock does not process the detected signal to produce an audible response, nor does it provide for signal attenuation after the initial pre-amplification stage.
A portable device which has been used in the past to detect ultrasonic energy is the UE 10,000 made by U.E. Systems of Elmsford, N.Y. This device is covered by U.S. Pat. No. 6,707,762, U.S. Pat. No. 6,804,992 and U.S. Pat. No. 6,996,030 to Goodman et al, which are incorporated herein by reference in their entirety. The UP 10,000 detects ultrasonic signals from deteriorated bearings and demodulates or heterodynes the signals to the audio range. These signals can then be heard by an operator through headphones or the signal can be viewed on a display as a way of detecting malfunctions. The heterodyned audio signal can be saved and later downloaded to an external spectrum analyzer in order to make more precise determinations of the status of the bearings. However, the applications identified above with Ser. Nos. 13/088,195 and 13/088,212 disclose spectrum analysis using Fast Fourier Transform (FFT) analysis directly on a light weight portable ultrasonic detection device.